34 Frank J. Schwartz 



with time (Coen and Heck 1991, Sutherland 1982, Peterson and Quammen 

 1982). 



I document clam siphon tip nipping by 14 species of fishes captured 

 at 22 stations in the Cape Fear River system of North Carolina during 

 intensive gill net and otter trawl samplings (10,646 efforts) between 

 1973 and 1978 and discuss the impact by size of fish, station, month, 

 year, and species. 



STUDY AREA AND METHODS 



The Cape Fear River south of Wilmington, North Carolina, is 

 an estuarine system that lies entirely within, and is the largest river 

 drainage to the Atlantic Ocean, in North Carolina (Schwartz et al. 

 1982). A study area was a 7,854-ha portion of the river south of Wilmington 

 that varied 1.6-3.6 km wide, is 17 km long, and daily is subject to 

 ±2 m tides that are affected by prevailing southeast or southwest winds 

 during nine months of the year. It included the main river from Buoy 

 42, just south of Wilmington, and near Campbell Island, southward 

 for 17 km to the ocean, and nearby Carolina Beach Inlet, Masonboro 

 Sound (Fig. 1). (See Schwartz et al. 1979a, b; 1982) for further habitat 

 and ecological details and descriptions.) 



Yearly 22 stations (Fig. 1) were sampled, during daylight hours 

 of 1973 through 1978, 10,646 times (2,362 gill nets sets; 8,284 otter 

 trawl tows). Sampling occurred twice each January, weekly sampling 

 occurred February through May and September through November, 

 and half of December. Single monthly samplings occurred in June, 

 July, and August of each year. Each shoal and intake canal station 

 was sampled for pelagic species using 8.7-cm x 91.4-m gill nets set 

 12 hours. Semi-balloon 7.6-m (all shoal and intake canal stations) 

 and 12.6-m (all shoal, channel, intake canal, and ocean stations) 1.9- 

 cm-stretched mesh otter trawls towed 0.3 hour were used to capture 

 all other species. A total of 2,013,986 fishes, within 57 families and 

 173 species, were collected. Entire small catches were kept, whereas 

 large catches were subsampled using a 8.5-L pail. The resultant mixed 

 catches and subsamples were immediately preserved in 10% formalin 

 and later sorted in the lab. Remaining specimens of large catches 

 were further subsampled for total number and mass, and returned alive 

 to each original capture site. Eighty-four species and 798,607 specimens 

 (39.7%) of the total were measured (standard length in millimeters, 

 SL) weighed (0.1 gm), and examined- for food content (Table 1). These 

 had been obtained following sampling all stations, except Buoy 42 

 (80 times) and the ocean (1,056 times) (range 222-744 times/station; 

 Table 2). 



